That's right, I only made a payment when I pre-ordered (for the keyboard plus a set of white keycaps).
At some point I received an email asking to confirm my address, so I replied to that.
And then, a few weeks later, I received the keyboard in the mail.
I'm not sure which wave I'm in.
My guess is that iMav used some of the money I paid for the set of white keycaps to cover the shipping. When the white keycaps will be available, he will probably contact me (and everybody else) and ask for payment to cover the remainder of the cost.
(this is just me guessing, since I don't know anything more)